The introduction of additional standardized cat extracts has resulted in a re-evaluation of these extracts, and the allergic response to the extracts. Cat extracts now may contain: (a) pelt, (b) pelt, hair and dander, (c) hair and dander, (d) concentrated cat wash, or (e) any mix of these materials as defined in the product. The current release test for potency of cat extracts is a radial immunodiffusion test for Fel d 1 content that measures one of the primary allergens of cat. Due to variability in source material, differences in protein and non-Fel d 1 allergen levels have been detected in assays developed by LAP. Two new assays are being developed to examine the relative quantity of cat serum in standardized cat extracts using the RAST inhibition and a Fluorescent Relative Potency(FRP) tests. Isoelectric Focusing(IEF) and Blotted RadioImmuno ElectroFocusing (BRIEF) procedures are also being utilized to evaluate these cat extracts. Preliminary work with these procedures suggests that possible significant compositional differences may exist between extracts. Review of these data is still in progress to determine the significance of these findings.